Compression hip and bone screw devices for use in fixating a fractured bone during the healing process have been used for years. Referring to FIG. 1, the typical device 10 used for hip fractures uses a lag screw 22 that is inserted into a femur 12 and used with a fixed side plate 24 which is attached to the femoral shaft 16. The lag screw is secured in the femoral head 14 on one end and abuttingly engages the barrel on the other end using a compression member or screw 28 thereby placing the femoral head/neck in axial compression across a bone fracture 27 placing the separated portions of the femoral head, neck or shaft area in contact for healing of the fracture. See for example U.S. Pat. Nos. 4,612,920 and 5,484,439.
The typical hip screw 10 is installed in a patient by making a large incision in the patient adjacent the proximal femur or outer hip. A guide is used to angularly position a guide wire, commonly at 135° with respect to femoral shaft, to penetrate the cortex of the femur and drive the guide wire across the bone fracture to position the wire in the cancellous bone within the femoral head. Using the positioned guide wire, a drill is used to ream a hole in the cortex for receipt of the lag screw 22 and side plate barrel to extend through the cortex. The lag screw and side plate are inserted through the large incision with the guide wire directing the position the barrel and lag screw. The lag screw is inserted along the guide wire and threadingly secured in the femoral head. The side plate is secured to the femoral shaft and a compression screw 28 engaged on the exposed end of the lag screw 22 against the barrel to place the lag screw in tension and the fractured bone pieces in compression across the fracture.
The prior art devices and methods suffer from several disadvantages in installation, adjustability and short and long-term effectiveness. Prior art lag screw and adjoining compression screws may provide sufficient initial compression forces across the bone, but suffer the significant disadvantage of losing compressive force capability and effectiveness over a very short period of time through common bone resorption or actual shrinkage of the bone across the fracture during the initial phases of the bone healing process.
Prior art side plates and integral, fixed barrels suffer from disadvantages of requiring a long incision to accommodate the long, downstanding side plate along the femoral shaft and the angular oriented barrel 26 is fixed in the anterior, posterior, medial and lateral planes. The fixed angular orientation and close concentrical relationship between the barrel and lag screw provide little or no adjustment in the event of a malaligned lag screw or side plate. This can result in improper alignment of the lag screw in the side plate barrel which, over time, can loosen, cause cut-out of the lag screw in the femoral head, bind the lag screw in the barrel or cause improper transfer of load on the device. The long and fixed barrel 26 extending through the cortex requires a larger bore in the bone and increased trauma to the area.
Thus, it would be desirable to provide a compression bone screw device to improve on the prior art disadvantages. It is further desirable to provide a bone screw device having a constant compression lag screw to maintain compressive force on the fractured bone throughout the healing process and beyond. It is further desirable to provide a minimally invasive side plate having an adjustable rollerball for receipt and adjustable alignment of the lag screw and side plate to promote proper alignment, adjustability, performance and long-term life of the device. It is further desirable to provide a side plate that is contoured to femoral anatomy to more evenly distribute loads and having a reduced downstanding portion to minimize the length of the incision in the patient.